Furnace.



' No. 757,442. 7 PATENTED APR. 19, 1904'.

S. G. DAVIDSON.

FURNACE,

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No.*.757', 442 "PATENTED APR .19, 190 i;

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FURNACE.

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in! I UNITED STATES Patented April 19, 1904.

PATENT OFFICE.

FURNACE.

SPECIFICATION forming part of Letters Patent No. 757,442, dated April19, 1904.

Application filed July 2, 1903. Serial No. 164,048. (No model.)

- To all whom, it may concern.-

Be it known that I, SAMUEL OLELAND DAVID- SON, a subject of the King ofGreat Britain and Ireland, residing in Belfast, Ireland, have inventedcertain new and useful Improvements in Furnaces, of which the followingis a specification.

In my Patent No. 682,674, dated September 17, 1901, I have described afurnace-front with a double wall forming an airchamber from which air issupplied to the furnace and to the ash-pit.

My present invention aims to provide a furnace-front showing certainpoints of improvement especially applicable to the type shown in saidpatent and also showing improvements applicable to other types offurnaces.

The principal objects of the present invention are to lengthen the lifeof the furnacefront, to facilitate the throwing of coal far into theback and the wings of the furnace, and to facilitate the passage of theair from one to another furnace when they are arranged as, for example,in the ordinary marine boilers. The improved furnace-front is alsosimplified in construction and presents other advantages in detailreferred to hereinafter.

The accompanying drawings illustrate the invention as embodied in afurnace for marine boilers.

Figure 1 is a front elevation. Fig. 2 is a horizontal cross-sectionapproximately on the line 2 2 of Fig. 1. Fig. 3 is a verticalapproximately central section. Fig. 4: is a horizontal section justabove the passages into the ash-pit. Fig. 5 is a vertical sectionapproximately on the line 5 5 of Fig. 3, illustratinga modification ofthe invention. Fig. 6 is a front elevation of the tube-box or shellsurrounding the doorway omitting the connected parts. Fig. 7 is a frontelevation of an ordinary marine boiler having three fur- According to myaforesaid patent the doorway comprising a short arched passage extendinglongitudinally of' the furnace was joined to the inner transverse wallat a sharp angle, approximately a right angle. The corner formed by themeeting of these lonprior patent.

gitudinal and transverse walls has been found in practice to obtain aconsiderably higher temperature than either of the walls, owing to theexposure of this corner to the heat of the fire on its two faces and tothe comparatively slow dissipation of the heat received by the veryrestricted surface of the interior of the angle inside the airchamber.The intense heat has frqeuently caused the metal at this point to burnaway. Furthermore, it has been found that the straight axial walls ofthe doorway render it diflicult for the stokers to throw the coal intothe wings or sides of the furnace.

According to the present improvement the walls of the doorway and thetransverse wall at the inner end of the doorway meet in a curve,preferably of as large a radius as the space will permit and preferablyconnecting the transverse Wall and the doorway-wall in one integralcasting. The doorway flares upwardly inward, so that, the stoker cangive a certain amount of elevation to the shovel full of coal as hethrows it in, and so facilitate throwing it. to the extreme back of thefurnace. Preferably the opening is flared laterally also, whichfacilitates the throwing of the coal into the extreme front corners ofthe wings of the furnace. Where the inner wall of the air-chamber andthe wall of the doorway are in one casting, the front plate of theair-chamber is preferably separate and attached by bolts to the inner ortop plate. Airtubes leading into the furnace are preferably providedsimilar to those described in my said Preferably the air from thechamber to the ash-pit leads through a valved passage or passages, sothat the relative quantities of air admitted to the furnace and theash-pit are under control. It has been found that the admission of airto the top of the furnace in the manner described sometimes causes aback sweep of the flame under the baflie plate of the door, where itrises between the door proper and the baflie-plate, heating the door toa too high temperature. In my present furnace provision is made to avoidthis action by the admission of air behind the baffle-plate.

Referring now to the drawings, A is the longitudinal wall of thedoorway, B the inner transverse wall, and C the outer or front wall.These three walls A, B, and 0 include the air-chamber D. The walls A andB meet in a curve E of such radius as to include nearly all of the wallsA and B themselves, at least at the top and sides of the opening. Theheat from the fire on the grate-bars F strikes the curved wall E and isequally distributed over it, so that there is no concentration at anyparticular point, while the inner face of the curve within theair-chamber is of sufficient length to dissipate the heat rapidly. Asindicated by the arrows G in Fig. 2, the lateral flare of the doorwayenables the stoker to throw the coal much more into the front part ofthe wings than with the prior straight-walled doorway. Likewise, asindicated by the arrow H in Fig. 3, the stoker can give a degree ofelevation to a shovel full of coal not possible with the priorconstruction, and so throw it much farther back into the furnace. Theair which in a marine boiler furnace may come down through funnels orthrough forced draft is admitted at one side of the chamber, as at J,Fig. 5, and where three or more furnaces are employed for a singleboiler the air after passing around the doorway passes out through theopposite opening J to the air-chamber of the adjacent furnace. Tubes orblowpipes K are mounted in the casting composing the plates A B andextend back into the air-chamber, so as to heat the air and direct it toa desired point in the furnace. The space D surrounds the doorway A onall sides and is made quite large, so as to present as little resistanceas possible to the passage of air therethrough from one of the openingsJ to the opposite opening. The openings J, as shown, run down nearly tothe top of the ash-pit door-opening, so as to give a straight passagefor the air between the bottom of the furnace door-opening and the topof the ash-pit door-opening. The portion of the chamber below thedoorway connects by passages L through a horizontal partition M with theash-pit. The passages are preferably valved, as by means of a slide N,with solid portions 0 a little wider than the passages L. The slide N isconnected by a link, as shown, to an arm on a shaft P, projectingthrough to the front and there provided with an operating-arm Q,carrying at its end on its under face a pin or rivet adapted to engageany one of the depressions or holes in the plate B, so as to hold thegrid-valve N in any position to which it may be moved.

Any suitable valve may be used for admitting the air from the chamber Dto the ashpit. For example, in Fig. 5 I show the horizontal partition Mprovided with two passages L, closed by gates or valves 0, pivoted attheir outer edges and swinging downward,

. so as not to interfere with the clear passage for the air above, andconnected to move together by suitable levers and links operated from ashaft P,which may extend through to the outside, like the shaft P,previously described.

The door may be provided with the usual or any suitable baflie plate S,spaced some distance within the door. In order to admit air within thespace between the door proper, T, and the baflie plate S, I preferablyprovide passages U, formed by grooves in the front face of thetube-plate A B and disposed around the top and sides of said plate, asindicated in Fig. 6. For the access of a greater quantity of air I maysubstitute or add additional tubes or blowpipes K, Fig. 2, or openingsV, Fig. 5, extending through the body of the plate A and preferablyvalved to regulate the quantity of air admitted according torequirements. For example, a pair of valves W might be applied, asshown, arranged to open and close together and under the control of anoperatinglever on the outside, similar to the lever for operating thegrid-valve described.

The front plate C and the surrounding ring X, as well as the horizontalpartition M, are preferably formed in one casting, which is bolted, asindicated, to the tube-plate at suitable intervals and to the innerash-pit plate Y, which engages the lower horizontal part of thedoor-opening A and which also carries the dead-plate Z, which supportsthe ends of the grate-bars F. The making of the plates Y and Z in onecasting simplifies the construction and the assembling or separation ofthe parts. The usual hand-holes are provided in the front plate C.

The furnace-door Tis hinged, as usual, upon lugs a, cast on the frontplate. Notched lugs 5 and '0 are provided at opposite sides of the door,the former being notched on its upper edge and the latter on its loweredge to engage an operating-bar (Z, pivoted on the outside of the door.The bar d is of the special shape shown in Fig. 2. At the end adjacentto the free edge of the door it is curved to provide a sort of handle 6,while at its opposite end it is bent around, as indicated at f.

A strap g is provided near each edge of the door, which overlies the endof the bar (Z and holds it close up to the door. The bar (Z is pivoted,as by a rivet h, the arm on the pivoted side of the door being a littleshorter than the other arm, so that the outer portion is always weighteddownward and the inner portion upward. Consequently when the door isslammed shut the outer arm of the bar (Z rides up over the inclinedupper edge of the lug b and drops into the notch, locking the door shut.When the outer end 6 is lifted and the door opened, the arm being thendropped the door swings back until the portion f, moving in the areindicated in dotted lines in Fig. 2, strikes the inclined under face ofthe lug c and engages in the notch, holding the door open at about theposition shown in dotted lines. The whole construction is very simpleand strong, so as to minimize the possibility of its getting out ororder.

The fire-pit door j is supported from lugs k on the front plate. Thestraps Z are hooked over the shaft m, running through the lugs 70, andthe door j is provided with handles n, by which it can be swung open orlifted off the shaft m. A bolt 0 at the lower edge serves for looking itclosed.

Fig. 7 shows the application of my invention to an ordinary marineboiler having three furnaces arranged in an ordinary manner. The airfrom a centrifugal fan or other suitable source enters by a tube A,leading into the air-chamber B of either furnace-front, as may be mostconvenient. The air circulates from the chamber of this furnace-frontinto the corresponding chambers of the other furnace-fronts through thepassages J J of Fig. 5. Any suitable communicating chamber or passagebetween the furnace-fronts may be provided. A suitable construction isto provide a single chamber inclosed between a front plate D and theboiler-front; but any construction by which the air admitted to thechamber D of one furnace-front may circulate into the correspondingchambers of the other furnace-fronts may be used.

Though I have described with great particularity of detail certainembodiments of the invention, yet it is to be understood that theinvention is not limited to the particular embodiments disclosed.Applications thereof to other types of boilers than that shown andvarious modifications 'in the details and in the arrangement andcombination of the parts may be made by those skilled in the art withoutdeparture from the invention.

What I claim is 1. A furnacefront having a detachable doorway and beingformed with an air-chamber entirely surrounding the lateral and top andbottom sides of said doorway, and leading to the furnace-fire, saiddoorway on the surface facing the fire being flared laterally andupwardly inward, and having tubular airpassages through said flaredsurfaces, to heat and admit air to the top surface of the fire from saidair-chamber.

2. A furnace-front having a detachable doorway and being formed with anair-chamber entirely surrounding the lateral and top and bottom sides ofsaid doorway, and leading to the furnace-fire, in combination with asubstantially horizontal and straight partitionplate extending from sideto side of said furnace-front, and separating the air-space which isbelow said detachable doorway from the ash-pit, and valved air-admissionports in said partition-plate for passage of air from said air-chamberinto the ash-pit.

3. A furnace-front having a detachable doorway and being formed with anair-chamber entirely surrounding the lateral and top and bottom sides ofsaid doorway, and leading to the furnace-fire, said doorway on thesurface facing the fire being flared laterally and upwardly inward, andhaving tubular airpassages through said flared surfaces, to heat andadmit air to the top surface of the fire from the said air-chamber, anda substantially horizontal and straight partition-plate extending fromside to side of said furnacefront and separating the air-space which isbelow said detachable doorway from the ashpit, and valved air-admissionports in said partition-plate for passage of air from said air-chamberinto the ash-pit.

4:. A furnace-front having a doorway, and being formed with anair-chamber surrounding said doorway on top, sides and bottom thereof,combined with a horizontal plate arranged below the bottom of saiddoorway, so as to leave a space between the two, an airadmission passagein said front arranged with a part of its effective opening below thebottom of said doorway, whereby air may be admitted directly to saidspace, and ports in said plate leading to the ash-pit.

5. A furnace-front having a doorway and an inner plate formed integrallywith each other, and an outer plate and surrounding ring formedintegrally with each other, said two parts being bolted together.

6. A furnace-front comprising a doorway and an inner plate formedintegrally with each other, an outer plate and surrounding ring formedintegrally with each other, and an inner ash-pit plate and dead-plateformed integrally with each other, said several parts being boltedtogether.

In witness whereof I have hereunto signed my name in the presence 'oftwo subscribing witnesses.

SAMUEL CLELAND DAVIDSON.

Witnesses;

THOMAS F. WALLACE, FRED WHITE.

